This invention relates to a small point of sale ink jet printer, and, in particular, to apparatus for periodically cleaning the nozzles of one or more ink cartridges that are reciprocally moved through the printing station of the machine.
Ink jet printers utilize ink cartridges, sometimes referred to as pens, which are arranged to dispense drops of ink onto a substrate such as paper to lay down a prescribed image as the carriage, in which one or more cartridges are supported, moves back and forth through a printing station. A cartridge generally contains a printhead having a series of small nozzles through which ink droplets are propelled onto the substrate. An ink ejection mechanism is located inside the cartridge that responds to input signals provided through terminals in the printhead to lay down the desired image.
In larger printers there is typically provided one or more nozzle cleaning stations containing wiper blades that are arranged to periodically move into contact with the nozzles to remove unwanted residual ink from the nozzle area before it can dry. The carriage, which can contain one or a plurality of ink cartridges, is programed to periodically move into the cleaning station or stations during each cleaning cycle. The cleaning station or stations are typically outside of the normal path of travel of the carriage and space for housing the wiper blade and related components is not a serious consideration. In a smaller point of sale printer, however, little space is available for a separate cleaning station. This space problem becomes more pronounced when more than one ink cartridge is mounted upon the carnage.
It is therefore an object of the present invention to improve relatively small point of sale ink jet printers.
It is a further object of the present invention to provide a compact nozzle cleaning mechanism for use in a small ink jet printer.
A still further object of the present invention is to provide a nozzle cleaning capability for a small two color point of sale ink jet printer containing a pair of ink cartridges mounted within a single carriage which does not require the range of movement of the carriage to be expanded beyond its normal printing range.
Another object of the present invention is to provide a compact, yet simple blade cleaning mechanism for wiping the nozzles of the ink cartridges of a two color ink jet printer.
These and other objects of the present invention are attained by means of a wiper blade cleaning mechanism that includes a rotor mounted for free rotation upon the main drive shaft of an ink jet printer upon which is mounted a drive roller that is used to advance a substrate through the printing station of the machine. The rotor, in one embodiment of the invention, is mounted immediately adjacent one end of the drive roller and is connected to an actuator through a rocker arm which moves the rotor between an inoperative position and an operative position. A wiper blade is mounted into said rotor that extends outwardly from the rotor""s rim. The blade is generally perpendicularly aligned with the path of travel of the ink cartridge carriage. When the rotor is in the operative position, the blade is adapted to engage the nozzles of an ink cartridge mounted in the carriage as the cartridge is reciprocated along the path of travel through the printing station. Placing the rotor in the inoperative position withdraws the blade out of the carriage""s path of travel and thus out of engagement with said ink cartridge nozzles.
In another embodiment of the invention a two color printer is equipped with a carriage containing two side-by-side ink cartridges. A pair of rotors are mounted on the drive roller shaft with each rotor being adjacent one end of the drive roller. The wiper blade of one rotor is adapted to clean the nozzles of an adjacent ink cartridge while the blade of the other rotor is adapted to clean the second ink cartridge as the carriage reciprocates over its normal path of travel.